Automatic electric traffic signal system



Sept. 13, 1938.

AUTOMATIC ELECTRIC TRAFFIC SIGNAL SYSTEM H. G. HUNTER 2,130,013

Filed June 8, 1936 3 Sheets-Sheet l 1; @Omg i G @M HH H @@@jg @oj I Emili! z S22/vera; Inferior l N SMQ/MO@ .Harry G Jlum/er Summe/59 Y Sept. 1-3, 1938., H. G. HUNTER AUTOMATIC ELECTRIC TRAFFIC SIGNAL SYSTEM 3 Sheets-Sheet 2 MUN-Dom Filed June 8, 1936 UW V31 Sept. 13, 1938. H. G. HUNTER AUTOMATIC ELECTRIC TRAFFIC SIGNAL SYSTEM 3 Sheets-Sheet 5 Filed June 8, 1936 n INVENTOR Hari? QHlller ATTORNEY Patented Sept. 13, 1938 AUTOMATIC ELECTRIC TRAFFIC SIGNAL SYSTEM Harry G. Hunter-Greensbord N. C. Application June. s, 193s, serial No. 84,194v

3 claims. p (ol. 1v1-339i My invention relates to improvements in automatic electric trac signal systems, 4and it consists in the combinations, construction, Aand arrangements herein described and claimed. 5 K My invention is particularly designed for use at dangerous intersections of highways, inthe country rather than the city streets althoughit could be used in the city where desirable.' j

An object of the invention is to provideza signal system, the use of which will speed uptraic without danger since it does not depend upon clock mechanisms which often cause unnecessary delays, but which is operated in accordance with the traic demands automatically.

A further object of the invention is to provide a system of the type described in which the protected intersection is'open for traifc upon one of the intersecting highways at all times, ulless a vehicle upon the other of said highways shall have energized a signal to be displayed which would then cause trailc upon the rst named highway to stop until the vehicle which actuated the signal cleared the crossing.

A further object of the invention is to provide a trafc signal system in which the signal lights,

automatically controlled by the vehicles approaching the'intersection upon one highway, will remain on for a predetermined period and will then be restored to normal condition.

A further object is to provide a signal system in which, if a number of vehicles are approaching vthe intersection upon one highway, the signals operated by the first one will be maintained by the succeeding vehicles, and in which the signal lights are only restored to normal when the last vehicle has cleared the intersection.

Other objects and advantages will appear in the following specification and the novel features of the invention will be particularly pointed out in the appended claims. v

My invention is illustrated in the accompanying drawings forming part ofA this application, in which:

Figure 1 is a diagrammatic view partly in perspective showing the intersecting highways and the location of the signal lights and the switches which control them,

Figures 2, 3, 4 and 5 are illustrations of the appearance of the lights under varying conditions, and

Figure 6 is a diagrammatic view of the circuits for operating the signal lights,

Figure 'I is an across-the-line diagram of Fig. 6. Referring now to Figure l, I have shown therein intersecting highways which I have indicated `as `Superior highway and Inferior highway with a signallingdevice S preferably suspended from poles p. In thel form illustrated, the lights of the signal S are controlled solely by the passage ofA vehicles alongl the Superior highway. It 5 will benoted that at a predetermined distance from the. intersectionv are the switches A'and B y for vehicles approaching from the left of Figure 1 .v SimilarswitchesA and B' are for vehicles approaching from the right in Figure 1. These l0 switchesare set far enough from the intersection to permit a vehicle traveling upon the Inferior highway at a maximum rate of speed to stop before reaching the intersection after the actuating vehicle upon the Superior highway has l5 crossed switch B (or B') thus causing the operation of the lights. The distance between the switches A and B and A and B' is determined by the time interval desired after the vehicle passes A and before it passes B (similarly for A' 20 and B). These pairs of switches function as a directional switch and may be combined in a single switch of special design. Y

In Figure 6 I have shown the circuits which are actuated by the closure of the switches A and B 25 `at the left of-the drawing and by the switches A' and B at the right of the drawing and in the central portion of the gure I have shown the circuits leading to the lights and the devices for controlling the same. 30

It will be observed that in the mechanism controlled by switches A and B I have provided a relay R, a time switch mechanism T, a multiple contact switch M and a second switch V. Similar mechanism is indicated at the right hand 3.; side of the drawing at R', T', M' and V', respectively;

For the controlling of the, lights I use a time limit relay G which will open a circuit after the lapse of a relatively long period of time follow- 40 ing the beginning of the passage of current through the relay. n This interval may be fteen seconds. A similar switch is shown at K. F is a multiple contact switch and H is a similar switch.

P indicates a delayed closing relay which closes 45 a circuit after delay of a relatively short period,

- say, one to two seconds, after current shall have begun to pass through the relay. O and W are electric contact switches and X, Y and Z indicate electric lamps. 50

In the drawings I have shown the Inferior highway as being open'to traiic unless the signals are set by trac along the Superior highway but it will .be understood that either highway might control the signals for the other. The 55 normal position of the apparatus is that shown in Figure 6. In this figure current from the source of power I passes through 2 to Z, contacts 3, 4, 5, 6 and by conductors 1 and 3 to line wire II. 'I'his energizes the red or "danger light Z for the Superior highway and the green or clear" light for the Inferior highway.

Now let us assume that a vehicle approaches on the Superior highway from the left. The switch A is traversed and the closure of the switch A sets up two circuits as follows:

(1) From the main line I through A, 9, coil of relay R, I0, coil of switch M, II and by I2 to power source II.

(2). From power source I, A, 3, R, I3, T, I4, II, I2 to II.

Three results follow:

(a) The contacts of the relay R are closed and locking circuits are set up from line I through I5, I5, I1, I3, I9, 20, R and by the paths already traced through the timing relay T and the coil of switch M, II and I2 to line II.

(b) The starting of the timing element of T, which is adjusted to open the locking circuits at I8 and I3 after a period of time determined by the time required for a vehicle traveling at a minimum predetermined speed to pass over the switch B.

(c) 'I'he closure of the contacts of the switch M at 2I-22, 23-24, and 25-25, but these closures do not set up circuits because of openings in these circuits at other points as will be described.

The vehicle next closes the switch B. This results in setting up of a circuit from the line I through 21, B, 28, 2i, 22, 29, coil of switch V and back to line II by conductor I2. The action of the switch V causes a circuit from line I, through 30, 23, 24, 3|, 32, 33, coil of switch F, 34, 35, 38, coil of time limit switch G, 31, 33, 39, 40, 26, 25 to line II. 'I'his circuit results in the (a) Starting of the time mechanism of the switch G and (b) Closes the switch contacts of the switch F. The latter action l (1) Sets up a locking circuit from the line I through 4I, 42, 43, 44, coil of delayed closing relay tion of time switch mechanism G in opening contacts 35 and 36.

(2) Sets up the signal circuit from the line I through 4I, 42, 43, 46, signal lamp X, 41, 43, 49, 53, and by 8 to line II.

(3) Sets up a circuit from lineI through 4I, 42, 43, 46, 5I, coil of switch O, 52, and to line II by the circuits already traced. When the switch O is actuated the contacts 3 and 4 are opened thus extinguishing the lamp Z.

(4) After the lapse of a selected period the delayed closing relay P closes its contacts by means of which H and K will function if the switches A and B are again operated before F and G are restored to normal. This operation will be explained later.

At the expiration of the predetermined period of time for which it is adjusted (this time being determined by the time required for a vehicle traveling at a selected rate of speed to travel from the switch B through the intersection), the time switch mechanism G opens the circuit at the contacts 35, 35, through the switch F which thereupon opens its contacts 43-42 and 43-4I, thus causing the system to return to normal.

For a second vehicle approaching upon the Superior highway either following the rst vehicle or traveling in the opposing lane and in the opposite direction .so that the second vehicle operates switches A and B or A' and B before the switch G shall have operated to restore the system to normal after the passage of the nrst vehicle, the following sequence occurs:

1. The system is in the actuated condition as described in paragraphs (1) to (4), inclusive, above.

2. 'Ihe second vehicle causes switch A to operate and perform the same functions described heretofore.

3. The second vehicle causes the corresponding switch B to operate instantaneously which sets up the same circuits as described previously but causes none of the devices in those circuits except switch V to operate because they are already energized and function as a result of the initial operation and In addition sets up the instantaneous circuit from line I, through 30, 23,'24, 3I, 32,

33, 45, 53, 54, 55, 55, coil of switch H, 51, 58, 5l,-

60, coil of relay K, 5I, 33, 39. 40, 28, 25 and by 62 to line II.

This results in the:

(a) Starting of the time mechanism of the relay K.

(b) Closes the switch H which (1) Sets up a locking circuit from line I through 2, 63, 64, 65, 88, coil of switch H, 51, 55, 55, 50, coil of relay K, 3|. 88, 59, 10, I2, 1 and 3 to line E.

(2) Sets up the signal circuit from line I through 2, 63, 54, 65, 61, signal lamp Y, 53, 53, 13, 82, 1, 3, to line II, thereby operating the signal Y.

(3) Sets up a circuit from line I, through 2, 53, 64, 55, 61, 12, coil of switch W, 13, and by 5l and the circuit previously traced to line II. When the switch W operates the circuit is broken at 5 and 6 so as to prevent the light Z from operating until the system is returned to normal.

At the expiration of a predetermined period of time for which it is adjusted (being determined by the time required for a vehicle travelling a selected rate of speed to travel from B through the intersection) the time switch mechanism K opens the circuit from the line I at the contacts 53 and 59, thereby de-energizing the circuit throughH and causing the system to return to normal.

In the event that a third vehicle should approach the system before the signal returns to normal, after its operationby the second vehicle but after the switch G shall have operated as a result of the passage ofthe first vehicle, the system operates as heretofore described for the first vehicle.

It will be seen that this system will permit vehicles on the Superior highway to pass in succession and to maintain a green light for clear passage while a red light will be maintained for the Inferior highway and after the traillc has cleared on the Superior highway then the various instrumentalities will be restored to normal so that the tramo on the Inferior highway may pass. When there is no traffic on the Superior highway the green light or clear passage will be displayed.

aiaacis The system will not be operated by vehicles travelling away from the intersection. Should such vehicles travel so far into the lane or lanes habitually used by opposing trafilc as to pass over the switches A and B, these switches will be closed but in the reverse order for operation. Since no means is provided to hold B closed until A is closed, it will immediately open and prevent the setting up of operating circuits. The switch A will remain closed for the time determined by the time limit relay T but this time is so short that the switch will be returned to its normal condition before-an approaching vehicle can reach it, as the vehicle which is travelling on the wrong side of the road will require more time to clear the traffic lane for the approaching vehicle than is required to release the circuits through the switches controlled by the relay T.

In Figure 1, as stated, I have shown two circuits which are actuated by switches on the runway, i. e., the switches A-B and A-B'. It will be apparent from an inspection of the drawings that a vehicle approaching from the right of Figure 1 will operate the switches precisely in the same manner as that already described as approaching from the left so that a description of the operation of one of the circuits will suiilce for both.

In Figs. 2 to 5, inclusive, I have shown the various conditions that exist. Figure 2 shows the normal condition with the danger signal Z showing on the Superior highway and the clear signal Z' showing on the Inferior highway. Both signals are displayed by energizing a single lamp which shows to the respective highways through properly placed colored lenses. In Figure 3 the condition is shown where there is one vehicle in the block on the Superior highway. At this time the light X, which indicates clear is shown on the Superior highway and the danger light X on the Inferior highway. These signals are displayed by a single lamp as above described in connection with signals Z and Z'.

In Figure 4 is shown the condition where there are two vehicles in the block. Here the clear lights X and Y are shown on the Superior high- Way while the two danger signals X' and Y' are shown on the Inferior highway.

In Figure 5 the condition is indicated where the second vehicle is in the block on the Superior highway when the first vehicle has cleared and in this instance the clear" signal Y is shownon the Superior highway and the danger signal Y' on the Inferior highway.

It will thus be seen that I have provided a system which is automatic and in which the delays occasioned by the holding up of trafiic, for instance, on a highway in the country where there are no vehicles even in sight on the intersecting highway, are obviated since, as stated. it is the presence of vehicles on one highway that controls the lights for a predetermined interval of time. After the lapse of an interval of time suilicient for these vehicles to have passed the intersection the system is restored to normal.

I claim:

1. An automatic electric tramc signal system for highway intersections comprising a "danger signal light normally displayed for one highway, a danger" signal light adapted to be displayed at tim'es for the other highway, a clear signal light normally displayed for the intersecting highway, a pair of clear signal lights adapted to be automatically displayed at times for the rstmentioned highway, a pair of roadway switches on one highway on each side of the intersection, the switches of each pair being spaced apart and being at a deiinite distance from the intersection, means actuated by the conjoint action of that pair of switches on the side of the intersection by approaching trame for changing the danger signal light to clear and the clear signal light to danger and including means which is adapted to be set in motion by a second vehicle passing over one of the pairs-of switches nearest the intersection for maintaining the danger signal for the second highway in operation while causing the second clear signal for the first-mentioned highway to be displayed, the means actuated by the conjoint action of the pair of switches also including means for delaying the cutting off of the clear signal light after both pairs of switches have been operated.

2. An automatic electric traffic signal system for highway intersections comprising a danger signal light normally displayed for one highway, a danger signal light adapted to be displayed at times for the other highway, a clear signal light normally displayed for the intersecting highway, a pair of clear signal lights adapted to be automatically displayed at times for the firstmentioned highway, a pair of roadway switches 0n one highway on each side of the intersection, the switches of each pair being spaced apart and being at a definite distance from the intersection, means actuated by the conjoint action of that pair of switches on the side of the intersection by approaching trafllc for changing the danger" signal light to clear and the clear signal light to danger, and including means which is adapted to be set in motion by a second vehicle passing over one of the pairs of switches nearest the intersection for maintaining the danger signal for the second highway in operation while causing the second clear signal for the mst-mentioned highway to be displayed, said switch-controlled means including timing mechanism for restoring the signals to their normal condition after a predetermined interval of time.

3. An automatic electric traffic signal system for highway intersections comprising a danger signal light normally displayed for one highway, a second "danger signal light adapted to be displayed at times for the other highway, a clear signal light normally displayed for the intersecting highway, a pair of clear" signal lights adapted to be displayed automatically for the rstmentioned highway, a pair of roadway switches on one highway on each side of the intersection, the switches of each pair being spaced apart and being at a definite distance from the intersection, said switches being actuated in a deiinite sequence by vehicles, means successively actuated by the conjoint action of the switches in proper sequence 0n the side of the intersection by approaching traic for changing the danger signal light to "clear and clear signal light to danger, and including means which is adapted to be set in motion by a second vehicle passing over one of the pairs of switches nearest the intersection for maintaining the "danger signal for the second highway in operation while causing the second clear signal for the ilrs't-mentioned highway to be displayed.

HARRY G. lHUlTTER. 

